A leading cause of failure in the clinical management of patients with congenital or acquired cardiovascular disease is the development of pulmonary vascular obstructive disease and pulmonary hypertension. Study is proposed of the natural history of pulmonary vascular disease in high flow left to right shunts in canine experimental models, with and without left atrial obstruction. Changes in the pulmonary vasculature will be observed using the analysis of instantaneous pulsatile pulmonary blood flow and pressure. The acquisition of this data is facilitated in the awake animal by chronic implantable electromagnetic flow probes, high-fidelity pressure micromanometers, and catheter-tipped flow probes. Data analysis will be fully computerized. It is anticipated that these more accurate and sensitive techniques for the analysis of the development of pulmonary vascular disease could contribute significantly to our understanding and therapeutic approach to this serious problem. It is anticipated that the techniques developed will eventually be applied to the assessment of clinical pulmonary vascular problems.